The present invention relates to flash event detection and, in particular, it concerns a flash detection system and method combining optical image sensing, range finding and acoustic sensing to reduce false alarm rates.
It is known to employ both optical and acoustic sensor systems, alone or in combination, to identify flash events. Examples of systems combining both optical and acoustic sensors may be found in U.S. Pat. Nos. 5,970,024, 6,215,731 and 6,621,764, all to Thomas Smith.
The principle mode of operation described by Smith in the aforementioned patents is the use of a microphone array to determine an initial estimate of the direction of an event. A gimbaled image sensor is then directed towards this direction and the location is verified optically during subsequent shots. Alternatively, plural optical sensors may provide a panoramic field of view and the detection results of the optical and acoustic systems are correlated to increase accuracy.
The aforementioned functionality described by Smith are reasonably effective under conditions of repetitive fire, but are unable to reliably detect the “first shot”. Furthermore, without any capability of determining the range of the flash event, it is impossible to reliably correlate data from the optical and acoustic subsystems so that one subsystem will verify the output of the other subsystem.
There is therefore a need for a flash event detection system and method which would determine an estimated range of an optically-detected tentative flash event so as to allow prediction of an expected time or arrival of a corresponding acoustic event, thereby allowing acoustic verification of an optical flash event even for a single shot.